The invention is generally related to the field of resist patterning of semiconductor devices and more specifically to resist strip and resist residue removal processes.
In the fabrication of semiconductor devices, photoresist patterns are routinely used for delineating certain areas of the semiconductor device, for example, for patterned etching and ion implantation. After the etch or implantation sequence, the resist pattern must be removed. This is referred to as a resist strip. Additionally, any resist residue must also be removed. Currently, an ozonated H2SO4 operated at 130xc2x0 C. or a combined solution of H2SO4 and H2 O2 are widely used for resist strip. To reduce particles, the above resist strip process is followed by a SC1 (H2O:NH4OH:H2 O2) megasonic cleanup. Alternatively, a deionized water (DIW) scrub may be used for particle removal.
Unfortunately, the chemicals described above for resist strip are not environmentally safe and require special precautions for handling and disposal. Furthermore, sulfur compounds have been found to be left on wafer surfaces after the H2SO4 cleanups, which may cause corrosions or work function shifts on devices. The SC1 clean-up may result in NH3 abatement. If the alternative DIW scrub is used, two process tools are required. Accordingly, a resist strip and particle removal process is desired that is environmentally safe and overcomes the above mentioned particle removal problems.
U.S. Pat. No. 5,464,480 describes a process for removing organic materials such as photoresist without the use of H2SO4 and H2 O2. Wafers are placed in a tank containing chilled deionized water. Ozone is diffused into the chilled deionized water to oxidize the organic material from the wafer surface. This process requires the addition of a chiller to current process equipment.
One aspect of the invention is a combined resist strip and particle removal process that uses ozonated deionized water at elevated temperatures in a scrubber. Both resist strip and particle removal are accomplished using a single scrubber step instead of two steps (a bench resist strip and a megasonic cleanup for particle removal).
Another aspect of the invention is a canister for use in forming the ozonated deionized water. The canister is filled with deionized water. The deionized water is circulated through the canister and ozone is added at a premixer stage. A dissolved ozone monitor may be used to monitor the ozone level and shut off the ozone when the ozone concentration reaches a set point.
An advantage of the invention is providing a single step resist strip and particle removal process that is environmentally safe.